Leeds United fans have been allocated only 1,000 tickets for the tie at The Den. Photograph: Jason Cairnduff/Action Images

"The fans like a scrap. We're looking forward to it. There has been more said about the fans fighting than there has been about the game."

At 12.45pm today 1,000 Leeds United supporters will take their seats to watch Simon Grayson's team start the first leg of their League One semi-final play-off with Millwall. Many more of the faithful would have made the trip – The Den can hold 4,600 away fans – but concerns over potential trouble from clubs historically plagued by an unwanted, violence-seeking minority have limited the numbers allowed in the away section.

The above comment is from Jason Price, Millwall's on-loan striker from Doncaster, who is a key figure today. He made the remark with a smile in his eyes. But, as with all jest, it holds an element of truth. The 32-year-old, who has scored three times in eight games since arriving in March, is looking forward to the game, not any ­potential trouble. There is enough concern, however, for the Metropolitan Police to deploy a 400-strong force in and around the stadium as the focal point of a "pan-London" strategy. When Millwall make the reverse trip on Thursday they are also limited to taking 1,000 fans.

Sources at The Den say they would have preferred more but West Yorkshire Police were uneasy about the encounter. Both clubs have been careful to ensure the tickets have gone to supporters who prefer football to seeking conflict in the area or in central London flashpoints, such as Covent Garden or Carnaby Street.

"The tickets have been distributed among our most loyal fans – anybody who has one had to have attended at least 18 away games," said Shaun Harvey, the Leeds United chief executive. "It would have been exceptionally easy to have no visiting supporters. But both clubs felt this would create the wrong impression for what is arguably the biggest game of the season. We feel as confident as we can be."

For Leeds, the last champions of the old First Division in 1992, it certainly appears the most crucial tie of their recent history. "Leeds United could've comfortably sold more than 1,000 for an away semi-final leg," Harvey added. "But clubs can't arbitrarily decide to give out tickets – this has been done in consultation with the respective police forces and the safety advisory groups at both clubs."

Earlier this season United brought 2,000 fans to south-east London and there was, the clubs say, little incident. "I don't see a problem today," said George Lampey of the Millwall supporters' club. How does he view the allocation of 1,000? "It's an even distribution and is slightly unfair to Leeds given they have a bigger fan base."

Any fears that local pubs might attract trouble from those not arriving by official coaches seem to hold little credence. There is a dedicated walkway from South Bermondsey station to the ground on match days. And the sum total of drinking venues nearby is nil. "The pubs have all closed down or been turned into housing developments," Lampey said. "Normally you can drink at the Den." Despite this apparent lack of opportunity for booze-fuelled strife the Metropolitan Police is taking no chances.

"We want to send a clear message to all fans that we'll police fairly but firmly to ensure the game passes without incident," said Superintendent Peter Vincent. "If you're coming to enjoy the game safely and legally we'll endeavour to help. However, if you intend to cause trouble you will find your efforts thwarted. It's also our aim to ensure that local residents and communities are able to go about their business safely and with the minimum level of necessary disruption."

This last comment suggests the police are acutely aware that football's most serious recent episode of violence occurred right in this manor, following the previous occasion Millwall were involved in a play-off. Seven years ago a 1–0 defeat by Birmingham City ignited a mob of around 900 fans who fought in the streets around The Den, injuring 100 police. Neil Harris, who played in the game and again lines up today, understands the sensitivities but feels more fans should have had the opportunity to attend this afternoon.

"There's a restriction on away fans for both clubs and that's a shame for the true fans who want to come to football. It stops 3,000 Millwall and 3,000 Leeds going to the away game and it detracts from the atmosphere in the ground."

He does, however, expect the usual Millwall welcome for United. "I'd be amazed if it's not a fantastic atmosphere on Saturday and next Thursday – it's why you play football.

"I think both grounds will be rocking with excitement and anticipation. It just adds spice to the games, the atmosphere will be a joy to play in. Our focus is on the pitch, what happens off is out of our control. So I'd rather it was between the two clubs on the pitch than off."